1. Field of the Invention
This invention relates to a resistance device for a bicycle exerciser, more particularly to a wheel-type resistance device which can provide an adjustable magnetic resisting force to the bicycle exerciser.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional wheel-type resistance device for a bicycle exerciser is shown to include a flywheel 1 mounted on a bicycle frame 3 and driven to rotate by a pedaling action of a user. A magnet assembly 2 is mounted swingably on the frame 3 by a linkage assembly 4, and has two walls 202 disposed adjacent to two lateral walls of the flywheel 1 and having a plurality of magnets 201 mounted thereon. The linkage assembly 4 includes two parallel cranks 401 with lower ends 402 mounted rotatably on the frame 3 and upper ends 405 mounted rotatably on a coupler 403 secured on the magnet assembly 2. One of the cranks 401 is connected to one end of a connecting bar 404. The other end of the connecting bar 404 is connected to a sliding block 502 of an adjustment member 5. The sliding block 502 engages threadedly a guiding threaded bolt 501 which is rotated by a motor 503 to move the sliding block 502 so as to adjust the position of the magnet assembly 2 relative to the flywheel 1, thereby adjusting the resisting force of the magnet assembly 2 to the flywheel 1.
It is noted that the conventional resistance device has a complicated structure and is inconvenient to assemble. Moreover, use of the linkage assembly 4 and the adjustment member 5 involves increased manufacturing and maintenance costs.
The object of the present invention is to provide a wheel-type resistance device which has a fewer number of components, thereby reducing the manufacturing and maintenance costs.
According to this invention, the wheel-type resistance device includes a magnetically permeable flywheel which is mounted on and which is rotatable about an axle that is mounted on a frame of a bicycle exerciser and that extends in an axial direction. The flywheel is driven to rotate by a pedaling action of a user, and has two side walls opposite to each other in the axial direction. Right and left swing arms have pivot ends which are adapted to be mounted pivotally on the frame of the bicycle exerciser about a swing axis transverse to the axial direction and outboard to a respective one of the side walls of the flywheel, and swing ends which are disposed opposite to the pivot ends in a direction radial to the axle so as to swing relative to the pivot ends about the swing axis to be remote from or close to each other respectively in a first or second position. Each of the right and left swing arms further includes a mounting member which is disposed between the pivot and swing ends and which extends in the axial direction to terminate at a mounting surface that is remote from or close to the respective one of the side walls respectively in the first or second position. Two biasing members are disposed to bias the mounting surfaces of the right and left swing arms to move from the second position to the first position. A right magnet member is mounted on and is movable with the mounting surface of the right swing arm. A left magnetically attractive member is mounted on and is movable with the mounting surface of the left swing arm. Thus, the movement of the right magnet member and the left magnetically attractive member from the first position to the second position will cause an increased dragging force on the flywheel as a result of interaction between the magnetically permeable flywheel and an increased strength of magnetic field established between the right magnet member and the left magnetically attractive member. A force adjusting cable has two cable ends which are respectively and tensely connected to the swing ends of the right and left swing arms, and an intermediate portion which is disposed between the cable ends and which is adapted to be pullably disposed on the frame of the bicycle exerciser. The intermediate portion is operable to pull the swing ends to the second position, thereby bringing the right magnet member and the left magnetically attractive member to the second position against the action of the biasing members.